Scrutinized trashcans and handrails of New York’s subway infrastructure reveal that the system houses potential threats to health, such as yet-unstudied microorganisms, accompanied by more common bacteria leading to meningitis or food poisoning.

The majority of the microbes inhabiting the New York City subway
system are harmless, but in several parts of the city samples of
disease-causing bacteria can be found, estimated at 12 percent.
These include drug-resistant species, or even DNA fragments of
anthrax and Bubonic plague, both, however, at very low levels and
likely not alive.

What’s more, nearly half (48 percent) of the sequences of DNA
that had been collected couldn’t be identified by the National
Center for Biotechnology Information or the Centers for Disease
Control and Prevention.

The results of an ambitious year-and-a-half-long project,
demonstrated by an interactive “pathogen” urban map, were
published by New York’s Weill Cornell Medical College
researchers in the journal Cell Systems on Thursday.

According to the study's senior investigator, Christopher Mason,
repeated “PathoMap” sampling could be used for
“long-term, accurate disease surveillance, bioterrorism
threat mitigation, and large scale health management for New
York”.

"Our data show evidence that most bacteria in these densely
populated, highly-trafficked transit areas are neutral to human
health, and much of it is commonly found on the skin or in the
gastrointestinal tract," Mason said in a
press release. "These bacteria may even be helpful, since
they can out-compete any dangerous bacteria."

The researchers collected DNA samples using nylon swabs inside
the trains, as well as in all open subway stations in 24 subway
lines across the five boroughs – and even the closed South Ferry
station, which was damaged by Superstorm Sandy in 2012. They were
also equipped with a specially designed mobile app, to log the
data on precise time and location of each sample.

“We built maps that detail what organisms are present in each
area of the city, creating a molecular portrait of the
metropolis,” said co-lead author Cem Meydan.

The international team of scientists also managed to find
positive correlations between demographic data and human DNA
samples found. They could trace the density of population, as
well as the ethnicity of the neighborhood. For instance, a
Hispanic area near Chinatown in Manhattan “appeared to hold a
strong mixture of Asian and Hispanic human genes.”

In 2013, New York City's subway system was used by an average of
5.5 million people per day, according to the city's Metropolitan
Transportation Authority.

“You wouldn't want to lick all the poles, even though you'd
probably be fine,” Mason told Gothamist blog. “Wash your
hands and don't walk around with a gaping wound.”

The study also has collaborators across the country, who have
collected samples from airports, subways, transit hubs, taxis and
public parks located in 14 states, including Texas and
California. The scientists hope that sequencing of the DNA to be
collected in the future, they will be able to compare the
country’s major urban areas.

Microorganisms comprise an important factor of human health, as
there are 10 times as many microbes as human cells, and their
function include resistance of various infectious diseases,
regulation of metabolism and even obesity risk control.